In SQL, what is the effect of the TRUNCATE TABLE statement?

To shorten all textual values in a column to a specified number of characters

To drop all of the columns defined on a table

EXPLANATION

TRUNCATE TABLE table-name;

TRUNCATE
removes all of the rows from the specified table without logging the
individual row deletions, without scanning the table, and makes freed
disk space available to the operating system immediately, without
requiring a subsequent VACUUM operation.
TRUNCATE TABLE is
similar to a DELETE statement with no WHERE clause, which also removes
all of the rows from a table; however, TRUNCATE is faster and uses fewer
resources. TRUNCATE is most useful when working with very large tables
where an unqualified DELETE could adversely affect database performance.

Tuesday, November 20, 2018

Which of these is an advantage of Manchester Encoding?

It uses less bits than the original signal

It is named after an English City

Very easy to understand

The signal is self-synchronizing

EXPLANATION

"In data transmission, Manchester encoding is a form
of digital encoding in which data bits are represented by transitions
from one logical state to the other. This is different from the more
common method of encoding, in which a bit is represented by either a
high state such as +5 volts or a low state such as 0 volts".
"The chief advantage of Manchester Encoding is the fact that the signal synchronizes itself." (See link for further reading).

Tuesday, November 13, 2018

Which of these files will not fit in a 32GB flashdrive formatted as FAT32?

10 .msi files with 1000MB each

A .zip file with 1024MB

3 .tar.gz files with 5GB each

All of them would fit just fine

EXPLANATION

Since your flash drive is formatted with the FAT32 file
system, any file that is larger than 4GB will not be placed there. This
type of a file system has a built-in limitation on the size of the files
that it may contain. Although the total size of the files that you can
copy to a FAT32 drive could be as large as 2TB (or the physical capacity
of the drive, whichever is smaller), the size of each individual file
may not exceed 4GB.
This limitation may sound silly: why would anyone design a system
that would not allow for the larger files? The problem is, when the
FAT32 file system was designed (that was back in the days of Windows
95), no one anticipated that we would have such large files in use
today. Or, maybe the designers hoped that by the time such large files
became common, the use of the FAT32 system would be replaced by more
modern systems.﻿

Which of the following is not an example of a denial-of-service attack?

Fraggle

Smurf

Teardrop

Roadrunner

EXPLANATION

Smurf / Smurfing

When conducting a smurf attack, attackers will use spoof their IP address to be the same as the victim’s IP address. This will cause great confusion on the victim’s network, and a massive flood of traffic will be sent to the victim’s networking device, if done correctly.

Most firewalls protect against smurf attacks, but if you do notice one, there are several things you can do. If you have access to the router your network or website is on, simply tell it to not forward packets to broadcast addresses. In a Cisco router, simply use the command: no ip directed-broadcast.

This won’t necessarily nullify the smurf attack, but it will greatly reduce the impact and also prevent your network or website from attacking others by passing on the attack. Optionally, you could upgrade your router to newer Cisco routers, which automatically filter out the spoofed IP addresses that smurf attacks rely on.

Fraggle

A Fraggle attack is exactly the same as a smurf attack, except that it uses the user datagram protocol, or UDP, rather than the more common transmission control protocol, or TCP. Fraggle attacks, like smurf attacks, are starting to become outdated and are commonly stopped by most firewalls or routers.

If indeed you think you are being plagued by a fraggle attack, simply block the echo port, located at port 7. You may also wish to block port 19, which is another commonly used fraggle exploitable port. This attack is generally less powerful than the smurf attack, since the TCP protocol is much more widely used than the UDP protocol.

Teardrop

In the teardrop attack, packet fragments are sent in a jumbled and confused order. When the receiving device attempts to reassemble them, it obviously won’t know how to handle the request. Older versions of operating systems will simply just crash when this occurs.

Operating systems such as Windows NT, Windows 95, and even Linux versions prior to version 2.1.63 are vulnerable to the teardrop attack. As stated earlier, upgrading your network hardware and software is the best way to stay secure from these types of attacks.

Fraggle, Smurf, and Teardrop are all actual denial-of-service attacks. Roadrunner is not.

Wednesday, November 7, 2018

Which of the following is the main purpose of a parked CPU core?

Saves Power

Increase performance of applications

Reserves CPU core for specific application process

To prolong the lifespan of the CPU

EXPLANATION

This process essentially puts your CPU cores in a sleep
state, and wakes them up when an application depends on higher core
usage. Majority of the time this is left enabled unless your a power
user or a gamer. It can increase performance slightly for those
situations. On some processors, this option cannot be disabled.

What do you call the feature in packet-based
data transmission protocols (Like TCP) that governs the amount of data
(number of packets) the receiver is able to accept from the sender?

Sequence Number

Jitter

CiDR

Sliding Window

EXPLANATION

The sliding window feature informs the sender how much data
(packets) the receiver can accept. Since networks are dynamic and are
prone to congestion this number fluctuates depending on a number of
variables. Essentially if my PC is sending a file to the server it may
send 10 packets out of 20,000 to start the transfer. If the server was
able to receive all of those packets it may request more.
This will
continue until the server either can't accept more because its buffer is
full or some packets were missed because of congestion. The sender
will then retransmit missed packets and begin to scale down the window
until the server and the receiver are in sync. This back and forth
continues to the end of the transfer.https://www.google.com/search?num=50&q=sliding+window+protocol&oq=Sliding+Window+pr&gs_l...

What is cgroups in modern Linux kernels?

A collection of tools that prevents malware using mandatory access controls policies

EXPLANATION

Cgroups (abbreviated from control groups) is a Linux
kernel feature that limits, accounts for, and isolates the resource
usage (CPU, memory, disk I/O, network, etc.) of a collection of
processes.
If you are using Docker give it a try! This may be useful for hungry Java apps ;)
See more at Wikipedia and kernel.org

What is the default TCP port used by Microsoft SQL server?

1433

3389

1723

987

EXPLANATION

The default (and IANA official port) for Microsoft SQL Server is TCP 1433.
Port 3389 is the default port for Microsoft RDP.
Port 1723 is the default port for PPTP VPN.
Port 987 is used by the Companyweb sharepoint site on Microsoft Small Business Server 2008 and later.